Global chronic total occlusion crossing algorithm: JACC state-of-the-Art review

JACC STATE-OF-THE-ART REVIEW Global Chronic Total Occlusion Crossing Algorithm JACC State-of-the-Art Review Eugene B. Wu, MD, a Emmanouil S. Brilakis, MD, PHD, b Kambis Mashayekhi, MD, c Etsuo Tsuchikane, MD, PHD, d Khaldoon Alaswad, MD, e Mario Araya, MD, f Alexandre Avran, MD, g Lorenzo Azzalini, MD, MSC,PHD, h Avtandil M. Babunashvili, MD, i Baktash Bayani, MD, j Michael Behnes, MD, k Ravinay Bhindi, MD, l Nicolas Boudou, MD, m Marouane Boukhris, MD, n Nenad Z. Bozinovic, MD, o Leszek Bryniarski, MD, p Alexander Bufe, MD, q Christopher E. Buller, MD, r,s M. Nicholas Burke, MD, b Achim Buttner, MD, s Pedro Cardoso, MD, t Mauro Carlino, MD, u Ji-Yan Chen, MD, v Evald Hoej Christiansen, MD, w Antonio Colombo, MD, x Kevin Croce, MD, PHD, y Felix Damas de los Santos, MD, MET, z Tony de Martini, MD, aa Joseph Dens, MD, PHD, bb Carlo di Mario, MD, cc Kefei Dou, MD, dd Mohaned Egred, MD, ee Basem Elbarouni, MD, ff Ahmed M. ElGuindy, MD, gg Javier Escaned, MD, hh Sergey Furkalo, MD, ii Andrea Gagnor, MD, jj Alfredo R. Galassi, MD, kk Roberto Garbo, MD, ll Gabriele Gasparini, MD, mm Junbo Ge, MD, nn Lei Ge, MD, nn Pravin Kumar Goel, MD, oo Omer Goktekin, MD, pp Nieves Gonzalo, MD, qq Luca Grancini, MD, rr Allison Hall, MD, ss Franklin Leonardo Hanna Quesada, MD, tt Colm Hanratty, MD, uu Stefan Harb, MD, vv Scott A. Harding, MD, ww Raja Hatem, MD, xx Jose P.S. Henriques, MD, yy David Hildick-Smith, MD, zz Jonathan M. Hill, MD, aaa Angela Hoye, MD, bbb Wissam Jaber, MD, ccc Farouc A. Jaffer, MD, PHD, ddd Yangsoo Jang, MD, eee Risto Jussila, MD, fff Artis Kalnins, MD, ggg Arun Kalyanasundaram, MD, MPH, hhh David E. Kandzari, MD, iii Hsien-Li Kao, MD, jjj Dimitri Karmpaliotis, MD, PHD, kkk Hussien Heshmat Kassem, MD, PHD, lll Jaikirshan Khatri, MD, mmm Paul Knaapen, MD, nnn Ran Kornowski, MD, ooo Oleg Krestyaninov, MD, ppp A.V. Ganesh Kumar, MD, qqq Pablo Manuel Lamelas, MD, MSC, rrr Seung-Whan Lee, MD, sss Thierry Lefevre, MD, ttt Raymond Leung, MD, uuu Yu Li, MD, vvv Yue Li, MD, www Soo-Teik Lim, MD, xxx Sidney Lo, MD, yyy William Lombardi, MD, zzz Anbukarasi Maran, MD, aaaa Margaret McEntegart, MD, PHD, bbbb Jeffrey Moses, MD, cccc Muhammad Munawar, MD, dddd Andres Navarro, MD, eeee Hung M. Ngo, MD, PHD, ffff William Nicholson, MD, gggg Anja Oksnes, MD, hhhh Goran K. Olivecrona, MD, PHD, iiii Lucio Padilla, MD, jjjj Mitul Patel, MD, kkkk Ashish Pershad, MD, llll Marin Postu, MD, mmmm Jie Qian, MD, nnnn Alexandre Quadros, MD, oooo Nidal Abi Rafeh, MD, pppp Truls Råmunddal, MD, PHD, qqqq Vithala Surya Prakasa Rao, MD, rrrr Nicolaus Reifart, MD, PHD, ssss Robert F. Riley, MD, tttt Stephane Rinfret, MD, uuuu Meruzhan Saghatelyan, MD, vvvv George Sianos, MD, PHD, wwww Elliot Smith, MD, xxxx Anthony Spaedy, MD, yyyy James Spratt, MD, zzzz Gregg Stone, MD, aaaaa Julian W. Strange, MD, bbbbb Khalid O. Tammam, MD, PHD, ccccc Craig A. Thompson, MD, ddddd Aurel Toma, MD, eeeee Jennifer A. Tremmel, MD, MS, fffff Ricardo Santiago Trinidad, MD, ggggg Imre Ungi, MD, PHD, hhhhh Minh Vo, MD, iiiii Vu Hoang Vu, MD, jjjjj Simon Walsh, MD, uu Gerald Werner, MD, kkkkk Jaroslaw Wojcik, MD, lllll Jason Wollmuth, MD, mmmmm Bo Xu, MD, nnnnn Masahisa Yamane, MD, ooooo Luiz F. Ybarra, MD, ppppp Robert W. Yeh, MD, qqqqq Qi Zhang, MD rrrrr From the a Prince of Wales Hospital, Chinese University Hong Kong, Hong Kong; b Minneapolis Heart Institute and Minneapolis Heart Institute Foundation, Minneapolis, Minnesota, USA; c Department of Cardiology and Angiology, II University Heart Center Freiburg, Bad Krozingen, Germany; d Toyohashi Heart Center, Aichi, Japan; e Edith and Benson Ford Heart and Vascular Institute, Henry Ford Hospital, Henry Ford Health System, Wayne State University, Detroit, Michigan, USA; f Clinica Alemana, Hospital Militar de Santiago, Santiago, Chile; g Pasteur Clinic Essey-lès-Nancy, Essey-lès-Nancy, France; h Division of Cardiology, VCU Health Pauley Heart Center, Virginia Commonwealth University, Richmond, Virginia, USA; i Center of Endosurgery, Moscow, Russia; j Cardiology Department, Mehr Hospital, Mashhad, Iran; k First Department of Medicine, University Medical Centre Mannheim, Faculty of Medicine Mannheim, University of Heidelberg, Heidelberg, Germany; l Royal North Shore Hospital, University of Sydney, Sydney, Australia; m Interventional Cardiology, Clinique Saint Augustin, Bordeaux, France; n Cardiology Department, Abderrahment Mami Hospital, Faculty of Medicine of Tunis, University of Tunis El Manar, Tunis, Tunisia; o University Clinical Ni s, Ni s, Serbia; p II Department of Cardiology and Cardiovascular Interventions, Institute of Cardiology, Jagiellonian University Medical College, Kraków, Poland; q Heart Center Krefeld, University Witten/Herdecke, Witten, Germany; r Teleflex, Markham, Ontario, Canada; s St. Michael’s Hospital, Toronto, Ontario, Canada; t Santa Maria University Hospital, Lisbon Academic Medical ISSN 0735-1097 https://doi.org/10.1016/j.jacc.2021.05.055 Listen to this manuscript’s audio summary by Editor-in-Chief Dr. Valentin Fuster on JACC.org. JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY VOL. 78, NO. 8, 2021 ª2021 THE AUTHORS. PUBLISHED BY ELSEVIER ON BEHALF OF THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION. THIS IS AN OPEN ACCESS ARTICLE UNDER THE CC BY-NC-ND LICENSE (http://creativecommons.org/licenses/by-nc-nd/4.0/). ABSTRACT The authors developed a global chronic total occlusion crossing algorithm following 10 steps: 1) dual angiography; 2) careful angiographic review focusing on proximal cap morphology, occlusion segment, distal vessel quality, and collateral circulation; 3) approaching proximal cap ambiguity using intravascular ultrasound, retrograde, and move-the-cap techniques; 4) approaching poor distal vessel quality using the retrograde approach and bifurcation at the distal cap by use of a dual-lumen catheter and intravascular ultrasound; 5) feasibility of retrograde crossing through grafts and septal and epicardial collateral vessels; 6) antegrade wiring strategies; 7) retrograde approach; 8) changing strategy when failing to achieve progress; 9) considering performing an investment procedure if crossing attempts fail; and 10) stopping when reaching high radiation or contrast dose or in case of long procedural time, occurrence of a serious complication, operator and patient fatigue, or lack of expertise or equipment. This algorithm can improve outcomes and expand discussion, research, and collaboration. (J Am Coll Cardiol 2021;78:840–853) © 2021 The Authors. Published by Elsevier on behalf of the American College of Cardiology Foundation. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Centre and Centro Cardiovascular da Universidade de Lisboa, Lisbon, Portugal; u Interventional Cardiology Unit, Cardio-ThoracicVascular Department, IRCCS, San Raffaele Scientific Institute, Milan, Italy; v Guangdong General Hospital, Guangdong, China; w Department of Cardiology, Aarhus University Hospital, Aarhus, Denmark; x Cardiology, Humanitas University, Humanitas IRCCS, Rozzano, Milan, Italy; y Cardiovascular Division, Brigham and Women’s Hospital, Boston, Massachusetts, USA; z Instituto Nacional de Cardiologia, Ignacio Chávez and Centro Medico ABC, Mexico City, Mexico; aa Advocate Heart Institute, Downers Grove, Illinois, USA; bb Hospital Oost-Limburg, Genk, Belgium; cc Department of Clinical & Experimental Medicine, University Hospital Careggi, Florence, Italy; dd Research Center for Coronary Heart Disease, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences, Beijing, China; ee Freeman Hospital & Newcastle University, Newcastle upon Tyne, UK; ff St. Boniface Hospital & University of Manitoba, Winnipeg, Manitoba, Canada; gg Department of Cardiology, Aswan Heart Centre, Magdi Yacoub Foundation, Aswan, Egypt; hh Hospital Clinico San Carlos, IdISSC, Complutense University of Madrid, Madrid, Spain; ii National Institute of Surgery and Transplantology NAMS, Kiev, Ukraine; jj Department of Invasive Cardiology, Maria Vittoria Hospital, Turin, Italy; kk Cardiovascular Medicine Department of PROMISE University of Palermo, Palermo, Italy; ll Maria Pia Hospital, GVM Care & Research, Turin, Italy; mm Department of Invasive Cardiology, Humanitas Clinical and Research Center, IRCCS, Rozzano, Italy; nn Zhongshan Hospital, Fudan University, Shanghai, China; oo Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India; pp Memorial Hospital, Istanbul, Turkey; qq Interventional Cardiology, Hospital Clinico San Carlos, IdISSC, Universidad Complutense, Madrid, Spain; rr Centro Cardiologico Monzino, IRCCS, Milan, Italy; ss Eastern Health/Memorial University of Newfoundland, St. John’s, Newfoundland, Canada; tt “Clinica Comfamiliar,”Pereira, Colombia; uu Belfast Health and Social Care Trust, Belfast, UK; vv Medical University of Graz, University Heart Center, Graz, Austria; ww Wellington Hospital, Capital and Coast District Health Board, Wellington, New Zealand; xx Hôpital du Sacré-Coeur de Montréal Université de Montréal, Montréal, Québec, Canada; yy University of Amsterdam, Amsterdam, the Netherlands; zz Sussex Cardiac Centre, Brighton, UK; aaa King’s College Hospital, London, UK; bbb Centre for Atherothrombosis and Metabolic Disease, Hull York Medical School, University of Hull, Hull, UK; ccc Emory University, Atlanta, Georgia, USA; ddd Cardiology Division, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA; eee Severance Cardiovascular Hospital, Yonsei University College of Medicine, Seoul, South Korea; fff Interventional Cardiology, Helsinki Heart Hospital, Helsinki, Finland; ggg Clinic of Cardiovascular Diseases, Riga East Clinical University Hospital, Riga, Latvia; hhh Promed Hospital, Chennai, India; iii Piedmont Heart Institute and Cardiovascular Services, Atlanta, Georgia, USA; jjj Department of Internal Medicine, Cardiology Division, Cardiovascular Center, National Taiwan University Hospital, Taipei, Taiwan; kkk Columbia University, New York, New York, USA; lll Kasr Alainy Medical School, Cairo University, Cairo, Egypt, and Fujairah Hospital, Ministry of Health, Fujairah, United Arab Emirates; mmm Cleveland Clinic, Cleveland, Ohio, USA; nnn Heart Center of the Amsterdam University Medical Centers, Amsterdam, the Netherlands; ooo Department of Cardiology, Rabin Medical Center, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; ppp Meshalkin Novosibirsk Research Institute, Novosibirsk, Russia; qqq Department of Cardiology, Dr. L.H. Hiranandani Hospital, Mumbai, India; rrr Instituto Cardiovascular de Buenos Aires, Buenos Aires, Argentina, and Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, Ontario, Canada; sss Department of Cardiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea; ttt Institut Cardiovasculaire Paris Sud, Hôpital Prive Jacques Cartier, Massy, France; uuu C.K. Hui Heart Centre, Royal Alexandra Hospital, Edmonton, Alberta, Canada; vvv Beijing Anzhen Hospital, Capital Medical University, Beijing, China; www Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China; xxx National Heart Centre of Singapore, Singapore; yyy Department of Cardiology, Liverpool Hospital and The University of New South Wales, Sydney, Australia; zzz University of Washington, Seattle, Washington, USA; aaaa Medical University of South Carolina, Ralph H. Johnson VA Medical Center, Charleston, South Carolina, USA; bbbb Golden Jubilee National Hospital, Glasgow, UK; cccc NewYork-Presbyterian/Columbia University Irving Medical Center, New York, New York, USA; dddd Binawaluya Cardiac Center and Department of Cardiology, Faculty of Medicine, Universitas Indonesia, Jakarta, Indonesia, and Department of Cardiology, Faculty of Medicine, Universitas Gadjahmada, Yogyakarta, Indonesia; eeee Hospital de los Valles, Hospital de Especialidades Eugenio Espejo, Universidad San Francisco de Quito, Quito, Ecuador; ffff Choray University JACC VOL. 78, NO. 8, 2021 Wu et al. AUGUST 24, 2021:840–853 Global Chronic Total Occlusion Algorithm 841 The success of chronic total occlusion (CTO) percutaneous coronary intervention (PCI) significantly improved during the past decade from 50%-70% (1)to 85%-94% (2-7) at experienced centers. In addition to technological advances, this improvement was catalyzed by the widespread implementation of an algorithmic approach to CTO crossing. The first CTO crossing algorithm was the hybrid algorithm (8)(Figure 1A, Table 1), which emphasized the importance of dual angiography and careful angiographic review to guide the selection of initial and subsequent crossing strategies. The hybrid algorithm also recommended a prompt change of strategy in case of failure to achieve progress and awareness of radiation and contrast use and procedure time. These guiding principles were adopted and expanded in subsequent algorithms (Table 1). The Asia Pacific CTO Club (APCTO) algorithm (9)(Figure 1B)recommended intravascular ultrasound (IVUS) to resolve ambiguity in the location of the proximal cap of the CTO, use of the CrossBoss catheter (Boston Scientific) for in-stent CTOs, use of parallel wiring, and consideration of tortuosity, calcification, and ambiguity for using a knuckle-wire technique. Similar algorithms were also published by the CTO Club China (10) (Figure 1C), the EuroCTO Club (11)(Figure 1D), and the Japan CTO Club (2). Existing algorithms have similarities but also significant differences (Table 1). Recently, a global consensus document highlighted 7 key principles of CTO PCI (12), 1 of which is that all CTO crossing techniques are valuable in the right setting. Development of a unified global CTO crossing algorithm could significantly facilitate decision making and CTO PCI teaching across various geographies and improve the safety, reproducibility, and efficiency of the procedure (13). An initial document draft of a global CTO crossing algorithm (Central Illustration, Table 1)wascreatedbyagroupof4CTO PCI experts from North America, Europe, and Asia. A total of 122 other CTO PCI experts from 50 countries were invited to participate, of whom 121 from 50 countries provided comments and approved this final document. The global CTO crossing algorithm includes the following 10 steps. STEP 1: DUAL ANGIOGRAPHY. Dual coronary angiography remains the cornerstone of CTO PCI and should be performed in nearly all cases unless the Hospital, Hochiminh City, Vietnam; gggg Emory Healthcare, Atlanta, Georgia, USA; hhhh Heart Department, Haukeland University Hospital, Bergen, Norway; iiii Department of Cardiology SUS-Lund, Lund University, Lund, Sweden; jjjj Department of Interventional Cardiology and Endovascular Therapeutics, ICBA, Instituto Cardiovascular, Buenos Aires, Argentina; kkkk Division of Cardiovascular Medicine, University of California, San Diego, School of Medicine, San Diego, California, USA; llll Chandler Regional Medical Center, Chandler, Arizona, USA; mmmm Cardiology Department, University of Medicine and Pharmacy “Carol Davila,” Institute of Cardiovascular Diseases “Prof Dr C.C. Iliescu,”Bucharest, Romania; nnnn Beijing Fuwai Hospital, Beijing, China; oooo Interventional Cardiology Division and Post Graduate Course of Cardiology, Instituto de Cardiologia do Rio Grande do Sul, Porto Alegre, Brazil; pppp St. George Hospital University Medical Center, Beirut, Lebanon, and North Oaks Healthcare System, Hammond, Louisiana, USA; qqqq Department of Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden; rrrr Care Hospitals, Hyderabad, India; ssss Department of Cardiology, Main Taunus Heart Institute, Bad Soden, Germany; tttt The Christ Hospital Health Network, Cincinnati, Ohio, USA; uuuu McGill University Health Centre, Montréal, Québec, Canada; vvvv Nork Marash MC, Erebouni MC, Yerevan, Armenia; wwww AHEPA University Hospital, Thessaloniki, Greece; xxxx Department of Cardiology, Barts Heart Centre, St. Bartholomew’s Hospital, London, UK; yyyy Boone Hospital Center, Columbia, Missouri, USA; zzzz St. George’s University Hospital NHS Foundation Trust, London, UK; aaaaa The Zena and Michael A. Wiener Cardiovascular Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA; bbbbb Bristol Royal Infirmary, University Hospital Bristol NHS Trust, Bristol, UK; ccccc Department at the International Medical Center, Jeddah, Saudi Arabia; ddddd NYU Langone Medical Center, New York, New York, USA; eeeee Department of Internal Medicine II, Division of Cardiology, Medical University of Vienna, Vienna, Austria; fffff Stanford University Medical Centre, Stanford, California, USA; ggggg PCI Cardiology Group, Bayamon, Puerto Rico, USA; hhhhh University of Szeged, Department of Invasive Cardiology, Szeged, Hungary; iiiii Royal Columbian Hospital, Vancouver, British Columbia, Canada; jjjjj Heart Center University Medical Center, Ho Chi Minh City, Vietnam; kkkkk Medizinische Klinik I Klinikum Darmstadt, Darmstadt, Germany; lllll Hospital of Invasive Cardiology IKARDIA, Nałe ˛czów/Lublin, Poland; mmmmm Providence Heart and Vascular Institute, Portland, Oregon, USA; nnnnn Fu Wai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences, Beijing, China; ooooo Saitima St. Luke’s International Hospital, Tokyo, Japan; ppppp London Health Sciences Centre, Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada; qqqqq Richard A. and Susan F. Smith Center for Outcomes Research in Cardiology, Division of Cardiovascular Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA; and the rrrrr Shanghai East Hospital, Tongji University, Shanghai, China. Javed Butler, MD, MPH, MBA, served as the Guest Editor-in-Chief for this paper. The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center. Manuscript received March 19, 2021; revised manuscript received April 16, 2021, accepted May 17, 2021. ABBREVIATIONS AND ACRONYMS ADR =antegrade dissection and re-entry APCTO =Asia Pacific CTO Club CTO =chronic total occlusion IVUS =intravascular ultrasound PCI =percutaneous coronary intervention Wu et al.JACC VOL. 78, NO. 8, 2021 Global Chronic Total Occlusion Algorithm AUGUST 24, 2021:840–853 842 collateral circulation originates exclusively from ipsilateral vessels. Dual angiography, with nitroglycerin if needed, facilitates planning of CTO crossing and guides crossing attemptsbyhelpingdetermine the guidewire position and detecting potential complications. Coronary computed tomographic angiography can also provide important information on CTO anatomy and procedural planning (14). Currently, most CTO techniques, including antegrade dissection and re-entry (ADR) techniques with the Stingray LP system (Boston Scientific) and simultaneous IVUS-controlled cap puncture or IVUS-guided wiring, can be performed with 7-F guide catheters using 7-F compatible equipment combinations, such as 5-F IVUS and low-profile microcatheters. Eight-French guide catheters are FIGURE 1 Different CTO Crossing Algorithms Retrograde6 3 1 54 Antegrade 7Switch Strategy Lesion length <20 mm noyes 2 1. Ambiguous proximal cap 2. Poor distal target 3. Appropriate “interventional” collaterals Hybrid A yesno Antegrade dissection and re-entry Controlled (Stingray) Wire based (LaST) Antegrade wiring Dual injection Retrograde dissection and re-entry Retrograde true lumen puncture (A) The hybrid algorithm. Reprinted with permission from Brilakis et al (8). (B) The Asia Pacific CTO Club (APCTO) algorithm. Reprinted with permission from Harding et al (9). (C) CTO Club China algorithm. Reprinted with permission from Junbo (10). (D) EuroCTO Club algorithm. Reprinted with permission from Galassi et al (11). ADR ¼antegrade dissection and re-entry; AWE antegrade wire escalation; BASE ¼balloon-assisted subintimal entry; CAG ¼coronary angiography; CART ¼controlled antegrade and retrograde tracking; CCTA ¼coronary computed tomographic angiography; CTO ¼chronic total occlusion; eGFR ¼estimated glomerular filtration rate; IVUS ¼intravascular ultrasound; KWT ¼kissing wire technique; LaST ¼limited antegrade subintimal tracking; POBA ¼plain old balloon angioplasty; RWE ¼retrograde wire escalation; SB ¼side branch; STAR ¼subintimal tracking and re-entry. Continued on the next page HIGHLIGHTS Several regional crossing algorithms for chronic total coronary artery occlusive lesions (CTO) have been published. The authors of these regional algorithms from 50 countries have collaborated in developing a global CTO crossing algorithm. This algorithm can encourage discussion, promote research collaboration, facilitate training and improve outcomes of percutaneous revascularization for patients with CTO. JACC VOL. 78, NO. 8, 2021 Wu et al. AUGUST 24, 2021:840–853 Global Chronic Total Occlusion Algorithm 843 still needed for more complex antegrade IVUS controlled re-entry cases and for ipsilateral singleguide retrograde cases with simultaneous IVUS guidance. Access choice depends on the balance of risk for vascular complication against potential benefits, especially in more complex CTO procedures. STEP 2: CAREFUL ANGIOGRAPHIC REVIEW. The coronary angiogram (most recent as well as prior angiograms)shouldbereviewedindetail,focusingon the following 4 characteristics. Proximal cap morphology. Clear understanding of proximal cap location is critical for safely attempting antegrade CTO crossing recanalization. Proximal cap ambiguityisakeyparameterintheglobalCTO crossing algorithm. CTOs with ambiguous proximal caps may be approached using the retrograde approach or IVUS or the “move-the-cap”subintimal crossing techniques, such as balloon-assisted subintimal entry or scratch and go (15). CTO lesion length and composition. Dual injection is necessary for estimating the occlusion length, as it allows visualization of the distal vessel and the distal cap. Calcification and tortuosity of the occluded segment increase the difficulty of CTO crossing and favor use of subintimal crossing techniques. Distal vessel quality. A distal vessel of large caliber ($2.0 mm) that fills well, does not have significant FIGURE 1 Continued APCTO B Careful analysis of angiogram/CCTA Proximal cap ambiguity Interventional collaterals present Retrograde approach Parallel wiring If suitable re-entry zone IVUS-guided wiring/LAST Consider use of CrossBossTM as primary crossing strategy Poor quality distal vessel or bifurcation at distal cap Antegrade wire based approach Dissection re-entry (Stingray SystemTM) IVUSguided entry Isolated occlusive in-stent restenosis Algorithm for CTO Crossing Yes Yes Yes Yes No No No No Consider stopping if >3 hours, >3.7 x eGFR ml contrast, Air Kerma >5 Gy unless procedure well advanced Consider primary use of KWT/ dissection re-entry Consider secondary use of KWT/ dissection re-entry • Ambiguous course of CTO • Tortuous CTO segment • Heavy calcification • Length >20 mm • Previous failed attempt Wu et al.JACC VOL. 78, NO. 8, 2021 Global Chronic Total Occlusion Algorithm AUGUST 24, 2021:840–853 844 disease, and is free from major branches facilitates CTO recanalization. Conversely, small, diffusely diseased distal vessels with significant bifurcations are more challenging to recanalize, especially after subintimal guidewire entry. Collateral circulation. Evaluation of the collateral circulation helps determine the feasibility of the retrograde approach. Retrograde access to the distal vessel can be obtained via septal collateral vessels, epicardial collateral vessels, or (patent or occluded) coronary bypass grafts. When assessing collateral vessels, it is important to consider size, tortuosity, bifurcations, angle of entry to and exit from the channel, and distance between the collateral exit and the distal cap. Larger collateral size and lack of tortuosity are associated with easier crossing by a guidewire and microcatheter (16,17). FIGURE 1 Continued CTO Club China Yes Yes No No Yes No Failed Failed Failed Failed Failed Failed Yes NoYes NoYes No Yes No No or failed IVUS-guided approach Yes C Simultaneous Bilateral CAG/CCTA No severe diffused distal lesion and/or no major SB near landing zone No severe diffused distal lesion and/or no major SB near landing zone Tapered Proximal Cap IVUS Guided Antegrade Approach Antegrade Approach Retrograde approach or IVUS Guided Suitable Collateral Channel Lesion length >20 mm Lesion length >20 mm Lesion length >20 mm Retrograde Approach ADR ADR Wire Escalation Parallel Wire Retrograde wire escalation or Kissing wire technique No severe diffused distal lesion and/or no major SB near landing zone Reverse CART ADR IVUS Guided JACC VOL. 78, NO. 8, 2021 Wu et al. AUGUST 24, 2021:840–853 Global Chronic Total Occlusion Algorithm 845 STEP 3: APPROACHING PROXIMAL CAP AMBIGUITY. Proximal cap ambiguity is inability to confidently determine the location of the proximal cap and is common in CTOs with a side branch at the proximal cap. A stiff-tip guidewire should not be used to puncture caps with proximal cap ambiguity. In some patients, proximal cap ambiguity can be resolved by performing angiography in different projections and FIGURE 1 Continued Euro CTO Club D Consider strategy switch when appropriate In−stent CTO Proximal cap ambiguity? Failure Failure Interventional collaterals? No NoYes No No Yes Yes Yes YesNo No Yes Bail−out strategy Possible as first line if CTO length >20 mm CTO length >20 mm? Severe calcification? Ambiguous vessel course? Failure to re−enter proximally Failure Failure Failure Poor distal vessel quality? Bifurcation at distal cap? *Such as: Δ BASE technique Δ Scratch and Go technique Δ IVUS guided puncture Consider CTO PCI failure in the following conditions, unless the procedure is well advanced: Δ Procedural time >3 hours Δ Contrast load >4 x eGFR (ml) Δ Air Kerma >5 Gy ** Investment procedure refers to deferred stenting (during a second procedure) after subintimal plaque modification via the STAR technique and balloon dilatation Dual injection Retrograde approach Knuckle wire technique RWE AWE CrossBossTM Parallel wire technique AWE ADR Stingray SystemTM Reverse CART Wire-based ADR: mini-STAR Investment procedure**: STAR+ POBA then deferred stenting Antegrade techniques to resolve proximal cap ambiguity* Wu et al.JACC VOL. 78, NO. 8, 2021 Global Chronic Total Occlusion Algorithm AUGUST 24, 2021:840–853 846 in others by contrast injection through a microcatheter near the suspected proximal cap. Coronary computed tomographic angiography can also help resolve proximal cap ambiguity. All current CTO crossing algorithms recommend a stepwise approach to proximal cap ambiguity: the hybrid algorithm recommends retrograde crossing, the APCTO algorithm recommends IVUS first followed by retrograde crossing if IVUS cannot clarify the anatomy, and the EuroCTO Club algorithm recommends IVUS or the “move-the-cap”subintimal techniques first, followed by retrograde crossing attempts. The global CTO crossing algorithm supports all 3 strategies (IVUS-guided puncture, “move-the-cap” techniques, and retrograde crossing) for approaching proximal cap ambiguity without prioritizing one strategy over another (Figures 2 and 3). Instead, the strategy that optimizes safety and increases the likelihood of success should be selected on the basis of CTO anatomy. For example, in cases of proximal cap ambiguity without an appropriate side branch for IVUS but with excellent septal collateral vessels, retrograde could often be the initial crossing strategy. In contrast, in proximal caps with a favorable side branch, IVUS-guided proximal cap puncture may be TABLE 1 Comparison of Various CTO Crossing Algorithms Hybrid Asia Pacific CTO Club EuroCTO Club CTO Club China Japan CTO Club Global 1. Dual angiography þþ þ þ þþ 1b. CTA þþ þ 2. Careful angiographic review þþ þ þ þþ ISR No specific recommendation þ(CrossBoss) þ(CrossBoss) þ(CrossBoss) Antegrade No specific recommendation; assess lesion characteristics and treat accordingly 3. Proximal cap ambiguity þþ þ þ þþ 3b. Solutions to proximal ambiguity Retrograde Retrograde, IVUS Retrograde, IVUS, move the cap Retrograde, IVUS, move the cap Retrograde IVUS, retrograde, move the cap 4. Poor distal vessel bifurcation distal cap þ(retrograde) þ(retrograde) þ(retrograde) þ(retrograde) þ(retrograde) 5. Retrograde option þþ þ þ þþ 6. Antegrade wiring strategies ADR for length $20 mm AWE, parallel wiring Primary ADR for ambiguous CTO course, tortuous CTO segment, heavy calcification Secondary ADR: length $ 20 mm, prior failed attempt AWE preferred; ADR possible as first line if length $ 20 mm ADR preferred if severe diffuse distal disease and major side branch near landing zone ADR or parallel wiring after AWE failure AWE preferred 7. Retrograde Ambiguous proximal cap, poor distal vessel þ interventional collateral vessels Ambiguous proximal cap (if IVUS fails), poor distal vessel þ interventional collateral vessels Ambiguous proximal cap, poor distal vessel þ interventional collateral vessels Ambiguous proximal cap þ no or failed IVUSguided approach þ interventional collateral vessels Reattempt, CTO length of $20 mm, and no stump þ interventional collateral vessels Ambiguous proximal cap, poor distal vessel þfeasible retrograde option 7b. RDR preferred over RWE Length $20 mm Length $15 mm Length $20 mm Severe calcification Ambiguous vessel course Length $20 mm Length $20 mm Severe calcification Ambiguous vessel course 7c. RDR preferred technique Reverse CART Contemporary reverse CART Reverse CART Reverse CART Reverse CART 8. Change þþ þ þAfter 20-min wire manipulation time þ 9. Investment þ þ 10. When to stop Air kerma >10 Gy Procedure duration >3h Air kerma >5Gy Contrast >3.7 eGFR Procedure duration > 3h Air kerma >5Gy Contrast >4eGFR Procedure duration >3h Procedure duration > 3h Air kerma >5Gy Contrast >3eGFR Complication ADR ¼antegrade dissection and re-entry; AWE ¼antegrade wire escalation; CART ¼controlled antegrade and retrograde tracking; CTA ¼computed tomographic angiography; CTO ¼chronic total occlusion; eGFR ¼estimated glomerular filtration rate; ISR ¼in-stent restenosis; IVUS ¼intravascular ultrasound; RDR ¼retrograde dissection and re-entry; RWE ¼retrograde wire escalation. JACC VOL. 78, NO. 8, 2021 Wu et al. AUGUST 24, 2021:840–853 Global Chronic Total Occlusion Algorithm 847 preferred. The “move-the-cap”techniques could be used if there are no significant side branches at the proximal or distal cap, as the intentional dissection can lead to occlusion of those branches, but should be avoided in patients with small and diffusely diseased distal vessels in whom re-entry into the distal true lumen may be challenging. STEP 4: APPROACHING POOR DISTAL VESSEL QUALITY OR BIFURCATION AT THE DISTAL CAP. In patients with poor distal vessel quality or bifurcation at the distal cap, the retrograde approach may be safer and more efficient for operators experienced in this technique (10). In patients with bifurcation at the distal cap, use of a dual-lumen microcatheter is recommended for advancing a guidewire into the side branch to prevent side branch occlusion after balloon angioplasty and stenting. If the CTO crossing guidewire position is unclear, IVUS should be performed before stent placement to avoid side branch occlusion due to subintimal position of the main branch wire at the bifurcation. STEP 5: FEASIBLE RETROGRADE OPTION. The term “interventional”collateral has been used for retrograde collateral vessels considered appropriate for crossing by the operator (8). Coronary bypass grafts, whether patent or occluded, are often used for the retrograde approach, eventhoughbypassgraftsare not truly “collateral”vessels. We introduce the term “feasible retrograde option”to describe the presence of any retrograde route considered appropriate for retrograde CTO PCI. Bypass grafts and septal collateral vessels are preferred over epicardial collateral CENTRAL ILLUSTRATION The Global Chronic Total Occlusion Crossing Algorithm 9. Investment Success 8. Change Strategy Move the cap Intravascular Ultrasound 3. Proximal cap ambiguity 4. Poor distal vessel quality 6. Antegrade wiring 1. Dual Injection 2. Careful analysis of angiogram 10. Consider stopping if >3 hours; 3x estimated glomerular filtration rate ml contrast; Air Kerma >5 Gy unless procedure well advanced. 7. Retrograde Approach 10. Stop 5. Feasible Retrograde Option Presence of Side Branch or FailFail No Yes No Fail FailFail Yes YesNo No No Yes Yes Yes 6b. Antegrade dissection and re-entry 6a. Parallel Wiring/ IVUS Wu, E.B. et al. J Am Coll Cardiol. 2021;78(8):840–853. Flow of chronic total occlusion crossing procedure. Yes or presence of feature or success indicated by green arrow; no or absence of feature indicated by red arrow; failure indicated by black arrow; progression to next step indicated by blue arrow. Wu et al.JACC VOL. 78, NO. 8, 2021 Global Chronic Total Occlusion Algorithm AUGUST 24, 2021:840–853 848